Feedback pressure responsive control valve for a rotary piston compressor

ABSTRACT

A pressure regulator for a rotary piston compressor. When the outlet pressure fed back to the suction side via line 24 exceeds a preset threshold, piston 14 urges stop 17 against the reciprocating, chamber defining slide 8, to thereby restrain the latter and prevent further compression. As the outlet pressure falls piston 14 and stop 17 move back to the left to release slide 8 and permit compression action to resume.

United States Patent [1 1 Riiedi et al.

[ FEEDBACK PRESSURE RESPONSIVE CONTROL VALVE FOR A ROTARY PISTON COMPRESSOR [75] Inventors: Joseph Riiedi, Birchwil, Switzerland;

()skar Vielmo, Sulzburg, Germany; Franz Weinhandl, Effretikon,

Switzerland [73] Assignee: Nova-Werke AG, Effretikon, lllnau,

Switzerland [22] Filed: Mar. 27, 1974 211 Appl. No.1 455,465

[ 1 Sept. 9, 1975 [56] References Cited UNITED STATES PATENTS 1,922,639 8/1933 Riesner 418/248 3,107,846 10/1963 Mihalakis. 1, 418/248 Primary Examiner-John J. Vrablik Attorney, Agenl, 0r FirmSughrue, Rothwell, Mion, Zinn & Macpeak [57] ABSTRACT A pressure regulator for a rotary piston compressor. When the outlet pressure fed back to the suction side via line 24 exceeds a preset threshold, piston 14 urges stop 17 against the reciprocating, chamber defining slide 8, to thereby restrain the latter and prevent further compression. As the outlet pressure falls piston 14 and stop 17 move back to the left to release slide 8 and permit compression action to resume.

6 Claims, 1 Drawing Figure a9 5 119 17 a m l 12 i7 15 2K 16a! 29 16 2a FEEDBACK PRESSURE RESPONSIVE CONTROL VALVE FOR A ROTARY PISTON COMPRESSOR BACKGROUND OF THE INVENTION 1. Field ofthe Invention The present invention relates to a rotary piston compressor comprising a piston located eccentric-ally with respect to its drive shaft and a stop slide pressed against the piston by at least one spring.

2. Description of the Prior Art Rotary piston compressors of this type are known. They may be used. for example. for producing com pressed air for compressed air brakes of vehicles. for example. heavy motor vehicles. When employed in this way. they are driven continuously by the motor of the vehicle and are designed to supply a compressed air brake cylinder with compressed air. The compressed air feed must be discontinued when there is a predetermined maximum pressure in the compressed air brake cylinder and it should be recommcnced when the coinpressed air in the cylinder falls below a lower threshold value. The process of switching into the idling state or of recommencing the compressed air supply is controlled by a special pressure regulator which. for CXIHTF le. opens and closes an auxiliary outlet valve.

SUMMARY OF THE INVENTION The object of the present invention is to provide a simplified pressure regulator for a rotary piston compressor of the type mentioned initially.

The present invention consists in that the stop slide is adapted to be held in its top compression point by a retaining piston which is adapted to be moved into its retaining position against the force of a first spring by a control piston acted on by feed pressure.

The retaining piston is advantageously connected to the control piston via a second spring.

To prevent the control piston from slowly exerting increasing pressure on the retaining piston as the feed pressure increases and vice-vcrsa. the control piston may adiantagcously be provided with a bistable lock ing mechanism with spring action. The retaining action on the stop slide thus begins suddenly and also ends suddenly when the feed pressure falls below a lower threshold value.

Rotary piston compressors are supplied with lubricatmg oil in a known manner. the lubricant being supplied from a pressure line via a dosing device controlled by the compressor. When the compressor is idling, that is. when the stop slide is retained in the top compression point and does not slide on the piston skirt surface, the supply of lubricant may be interrupted. It is therefore advantageous for the control piston to simultaneously constitute a distributing slide valve servo piston for the lubricating oil feed. To this end. the control piston may be provided with an annular groove which communi catcs with the lubricating oil feed line when the piston is in a position in which the stop slide is released.

Other objects. features and advantages of the present invention will be made apparent from the following dctailcd description of the preferred embodiment thereof pro\idcd in reference to the drawing which shows a cross sectional view of a rotary piston compressor.

DESCRIPTION OF THE PREFERRED EMBODIMENT The rotary piston compressor shown in the drawing tiU comprises a housing 1 in which is located a shaft 2 with an eccentric central part 3. An eccentric ball race 4 is mounted for rotation on the eccentric part 3. A rotary piston 5, the skirt surface of which touches the inner wall of the housing 1 along a line is mounted for rotation on the bearing ring 4. The friction surface between the bearing ring 4 and the rotary piston 5 is represented as a friction bearing 6. However. a roller bearing could also be provided. The generating space 7 of the compressor is divided by a stop slide 8 which is pressed against the rotary piston 5 by a spring 9 via a bolt 10. The air is sucked in through the inlet E on the one side of the stop slide 8 and enters the chamber 7 through an inlet port 7a adjacent the stop slide 8. It is then forced through a recess 11 on the other side of the stop slide 8 via a pressure valve 12 into the outlet A.

A housing 13 which contains an axially displaccable control piston 1-1 is also secured to the suction side of the housing. This control piston 14 comprises an extension having threading l5 and a ram 16 with a bore hole 161:. A retaining piston 17 is displaceably mounted in a stator bore in the axial extension of the ram [6. The front side of the retaining piston I7 is directed towards the stop slide 8. The piston 17 comprises a rod 17a bearing a spiral spring 18. The spring 18 is checked by an annular disc 19 and a spring washer 20. The annular front side of the ram 16 abuts against the annular disc 19. A lock nut 21 is provided on the threading 15. A prcstrcssed spiral spring 22 is arranged between the lock nut 21 and the housing 1. The space 23 in front of the control piston 14 is connected to the outlet side A via a line 24. On its inner side. the housing 13 is pro \ided with an outwardly extending inclined portion 25. Two bearings 26 stressed by a spring 27 are arranged in a cross bore of the control piston [4. When the piston I4 is in the position represented. the bearings 26 engage in an annular groove 30 in the housing 13. The control piston 14 also comprises an annular groove 28 which is in communication with a lubricating oil line 29 when the control piston is in the position shown in the drawing. The mode of operation of the rotary piston compressor is the following: The outlet A is connected. for example. to a compressed air brake cylinder of a vehicle. The compressed air in this brake cylinder and in the outlet A is also conveyed through the line 24 into the space 23. The compressed air thus acts on the control piston 14 and pushes it to the right against the pressure of the spring 22. When a predetermined air pres sure is exceeded. the control piston 14 is moved to the right. i.e.. against the stop slide 8 whereupon it presses the retaining piston 17 against the stop slide 8 via the spring 18. The bearings 26 then engage in the extension formed by the in lined portion 25. The stop slide 8 is now pressed by the rotating piston 5 into its top compression point. The force of the spring is no longer sufficient to move it downwards. The piston 5 thus ceases to supply compressed air. Through the displacement of the control piston I4 the oil feed through the line 29 is also interrupted. \Nhen the air pressure in the cylinder and thus in the supply line and in the space 23 now falls below a predetermined value. the spring 22 can again move the control piston 14 towards the left and the bearings 26 engage in the groove 30. The stop slide 8 is then released and the compressor begins to supply compressed air again. The feeding of lubricating oil to the compressor is simultaneously commenced.

The prcstrcssing of the spring 22 can be altered by turning the adjusting nut 21. In this way it is possible to adjust the value of the air pressure at which the control piston 14 responds.

What is claimed is:

I. In a rotary piston compressor having a piston located eccentrically with respect to its drive shaft and a stop slide pressed by at least one spring against the piston, the improvement comprising: a housing, a retaining piston adapted to hold said stop slide in its top compression point, a control piston in said housing adapted to actuate said retaining piston into its retaining position, a first spring urging said control piston away from said retaining piston and. a source of feed pressure to move said control piston against the force of said first spring whereby said retaining piston is moved into its retaining position.

2. A rotary compressor according to claim 1, wherein a second spring connects the retaining piston (17) to the control piston (14).

3. A rotary piston compressor according to claim 2, wherein a bistable locking mechanism locks the control piston (14) by spring action (26, 27).

4. A rotary piston compressor according to claim 3, wherein said bistable locking mechanism comprises. a plurality of bearings (26), said bearings stressed by a spring (27) and arranged in the control piston (14), said bearings (26) arranged for engagement in recesses in said housing (25, 30) at two end positions of the control piston (14).

5. A rotary piston compressor according to claim 1, wherein the control piston 14) further is a distributing slide valve servo piston for a lubricating oil feed.

6. A rotary piston compressor according to claim 5, wherein the control piston (14) comprises an annular groove (28) in communication with a lubricating oil supply line (29) when the control piston (14) is in the position in which the stop slide (8) is released. 

1. In a rotary piston compressor having a piston located eccentrically with respect to its drive shaft and a stop slide pressed by at least one spring against the piston, the improvement comprising: a housing, a retaining piston adapted to hold said stop slide in its top compression point, a control piston in said housing adapted to actuate said retaining piston into its retaining position, a first spring urging said control piston away from said retaining piston and, a source of feed pressure to move said control piston against the force of said first spring whereby said retaining piston is moved into its retaining position.
 2. A rotary compressor according to claim 1, wherein a second spring connects the retaining piston (17) to the control piston (14).
 3. A rotary piston compressor according to claim 2, wherein a bistable locking mechanism locks the control piston (14) by spring action (26, 27).
 4. A rotary piston compressor according to claim 3, wherein said bistable locking mechanism comprises, a plurality of bearings (26), said bearings stressed by a spring (27) and arranged in the control piston (14), said bearings (26) arranged for engagement in recesses in said housing (25, 30) at two end positions of the control piston (14).
 5. A rotary piston compressor according to claim 1, wherein the control piston (14) further is a distributing slide valve servo piston for a lubricating oil feed.
 6. A rotary piston compressor according to claim 5, wherein the control piston (14) comprises an annular groove (28) in communication with a lubricating oil supply line (29) when the control piston (14) is in the position in which the stop slide (8) is released. 